How to Convert Sea Level Pressure to Station Pressure

In weather reports, air pressure is reported in millibars at sea level. The actual air pressure, however, varies with both elevation and temperature. You can convert the reported (sea level) pressure to actual station pressure with an exponential equation.

Things You'll Need

• Calculator with exponential function

Instructions

1. Convert the elevation to meters, if necessary. To convert from feet to meters, multiply by 0.3048. For example, if you are at 5000 feet, that is equal to 1524 meters.

2. Convert the given temperature to degrees Kelvin. Scientists typically measure temperature in degrees Kelvin; this measure is always positive (0 degrees Kelvin is absolute zero) and are the same size as centigrade degrees. To convert from degrees Fahrenheit to degrees Kelvin, multiply by 5, divide by 9 and then add 273. So, 80 degrees Fahrenheit would equal:

   (80 * (5/9)) + 273 = 44.44 + 273 = 317.44 degrees Kelvin.

3. Multiply the temperature in degrees Kelvin by 29.263; in the example from Step 2, 317.44 * 29.263 = 9289.377.

4. Divide the elevation in meters by the product in Step 3. In the example, 1524 / 9289.377 = 0.164.

5. Multiply the quotient in Step 4 by -1. In the example, this becomes -0.164.

6. Raise e to the power of the result from Step 5. In the example, e^-0.164 = 1.178. Here e is the base of the natural logarithms. You can do this on a scientific calculator with a key that is marked e^x (or something similar).

7. Multiply the given sea level pressure by the result in Step 6; this is your station pressure. If, in the example, the reported pressure was 1000 millibars, the station pressure would be 1000 * 1.178 = 1178 millibars.

References

• Weather Prediction: Conversions
• Sandhurst Weather: Barometric Pressure